1. Field of Invention
Exemplary aspects of the present invention relate to an image forming apparatus, a process cartridge provided in the image forming apparatus, and a developing device included in the process cartridge of the image forming apparatus. More particularly, exemplary aspects of the present invention relate to an image forming apparatus that employs a process cartridge having a developing device to effectively regulate a thickness of a developer brought up onto a developer bearing member.
2. Discussion of Related Art
Related art image forming apparatuses widely use a two-component developer including non-magnetic toner and magnetic carrier. In such an image forming apparatus, toner is supplied from a toner supplying device to a developing device in which at least one agitating member mounted therein agitates the toner. The agitated toner is conveyed to a developer bearing member for developing an electrostatic latent image formed on an image bearing member to a visible image.
When the amount of developer accommodated in the developing device is too small, the height of the developer becomes low and a sufficient amount of toner cannot be supplied to the developer bearing member. This may cause a nonuniformity in pitches of the agitating member to adversely affect a reproduced image.
Since recent related art developing devices include a developer container or a developer containing space to hold a developer therein, a sufficient amount of developer cannot be accommodated in such limited space.
A related art developing device is provided with a toner guide in the vicinity of a toner supplying opening of a developer container so that toner supplied from a toner supplying device can be guided to developer accommodated in an upstream area of a rotation direction of a toner conveying screw provided in the developer container.
When two conveying screws are used to convey developer or carrier in an axial direction thereof, the toner supplied from the toner supplying device is conveyed to slide over the developer or carrier due to a difference in specific gravity of the toner and the developer or carrier. This reduces or eliminates a disadvantage that the toner and the developer cannot sufficiently be mixed or agitated. The above-described operation can uniformly distribute the toner in the developer. Thereby the related art developing device forms images without density nonuniformity and toner scattering.
The above-described related art developing device, however, takes the toner in the developer into the developer container. In this case, the amount of toner received from the toner supplying device may vary depending on the height or pressure of the developer. Further, the height of the developer cannot be sufficiently maintained due to a gap between a developer bearing member and the toner conveying screw. The above-described conditions may induce a nonuniformity in pitches of the toner conveying screw.